Tantalum

Original source: Filella, M., May, P.M., 2019. The aqueous solution thermodynamics of tantalum under conditions of environmental and biological interest. Applied Geochemistry 109, 104402.

Best stability constant values for tantalum species, 25 °C and I 0 mol L^-1:

Reaction	log K
Ta(OH)₅(s) = Ta(OH)₅⁰	–5.295
Ta₂O₅(s) + 5 H₂O = 2 Ta(OH)₅⁰	–20.00
Ta(OH)₅ + H⁺ = Ta(OH)₄⁺ + H₂O	0.7007
Ta₆O₁₉^8– + H⁺ = HTa₆O₁₉^7–	16.35
HTa₆O₁₉^7– + H⁺ = H₂Ta₆O₁₉^6–	14.00
Ta₂O₅(s) + 6 F^– + 4 H⁺ + H₂O = 2 TaF₃(OH)₃^–	8.886
Ta₂O₅(s) + 10 F^– + 10 H⁺ = 2 TaF₅⁰ + 5 H₂O	31.35
TaF₅ + F^– = TaF₆^–	3.003
TaF₆^– + F^– = TaF₇^2–	2.129
TaF₇^2– + F^– = TaF₈^3–	2.374
TaF₈^3– + F^– = TaF₉^4–	2.673

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